1. Field of the invention
The present invention relates to a visible light ray-curable (hardenable) monomeric composition for fastening loose teeth.
More particularly, the present invention relates to a visible light ray-curable monomeric composition for fastening or fixing loose natural tooth structures to each other or natural tooth structures to dental restoration materials, for example, metallic materials, organic polymeric materials and ceramic materials, with a high adhesion or bonding strength and an aesthetically pleasing appearance.
2. Description of the Related Art
It is known in the field of dentistry that carious tooth structures and defective tooth structures can be restored by using various types of dental restorative materials including metallic materials, for example, gold, silver, platinum, alloy and amalgam materials; organic polymeric materials, for example, polymethylmethacrylate, polycarbonate, cured polyfunctional vinyl polymer, and composite resin materials; and ceramic materials, for example, bore-selenium and other implant materials.
The above-mentioned materials do not have a property of an inherent adhesion to the natural tooth structures, and therefore, many attempts have been made to provide dental adhesion (bonding) agents containing at least one monomeric adhesive compound having a polar radical and capable of adhering dental restoration materials to natural tooth structures therethrough.
Some of the conventional adhering agents can effect the above-mentioned adhesion by curing an adhesive monomeric component in the presence of a redox curing agent (which is a mixture of an organic peroxide compound and an amine compound) or a photopolymerization initiator. Alternatively, other conventional adhering agents can be cured by mixing an adhesive monomeric component with a powdery filler immediately before application thereof, and curing the resultant mixture in the presence of a redox curing agent.
Where a loose tooth structure, e.g., one which is not firmly fixed to an alveolus dentalis due to an alveolitis, for example, pyrrhea alveolaris, is fastened to an adjacent tooth structure, an adhering agent is prepared by mixing and kneading an adhesive monomeric component with a powdery filler comprising an inorganic powder or an organic polymeric powder, outside of the mouth, inserted into gaps between the natural tooth structures, and solidified (hardened) to fix the tooth structures to each other.
Where a tooth structure is fixed to an orthodontic device, for example, a metallic orthodontic device, the adhering agent prepared in the abovementioned manner is inserted into gaps between the tooth structures and the orthodontic device and solidified (cured), and the orthodontic device is further fixed to the tooth structure by a binding wire.
When the conventional adhering agent is practically used, however, the mixing of the monomeric component and the powdery filler must be carried out immediately before the application thereof, and outside of the mouth. Thus, the conventional adhering agent is disadvantageous in that, since the mixture of the monomeric component and the filler is easily hardened (cured) within about 4 to about 7 minutes, the mixing operation must be carried out quickly within a very short time. This rapid mixing operation, however, causes the formation of a number of air bubbles in the resultant adhesive layer, and thus this resultant adhesive layer exhibits a poor mechanical strength.
Usually, a loose tooth structure is spaced from an adjacent tooth structure through a gap having a relatively large thickness, and to fasten the loose tooth structure to the adjacent tooth structure, the gap must be filled with an adhering agent. Namely, the adhering agent must form a thick adhering layer between the tooth structures. To ensure the formation of such a thick adhering layer, the adhering agent must have a high viscosity. It is difficult to obtain a conventional adhering agent consisting of an adhesive monomeric component alone and exhibiting a high viscosity. Also, even if a high viscosity adhering agent can be prepared by mixing a powdery filler into the adhesive monomeric component, it is very difficult to use the resultant adhering agent having a high viscosity in the mouth, and thus such an agent can be employed only by very skilled dentists.
Even if a thick adhering agent layer can be formed from the conventional adhering agent, the resultant thick adhering agent layer exhibits an unsatisfactory poor mechanical strength and surface hardness.
In a liquid-powder mixture type conventional adhering agent, the mixing ratio of the liquid component (adhesive monomeric component) to the powder component (filler) can be varied, but an increase in content of the liquid component results in a lower mechanical strength of the resultant adhering layer, whereas the adhesive strength of the resultant adhering layer to the natural tooth structures or artificial devices is increased. Also, an increase in the powder component content results in a lowered adhesive strength of the resultant adhering agent to the tooth structures or artificial devices, whereas the resultant adhering layer exhibits a high mechanical strength.
Accordingly, there is an urgent need for the provision of a dental adhering agent having a high adhesive strength to natural tooth structures and artificial dental devices and capable of forming an adhering layer having a high mechanical strength.